Symbol Message Passing Decoding of Nonbinary Low-Density Parity-Check Codes

We present a novel decoding algorithm for q-ary low-density parity-check codes, termed symbol message passing. The proposed algorithm can be seen as a generalization of Gallager B and the binary message passing algorithm by Lechner et al. to q-ary codes. We derive density evolution equations for the q-ary symmetric channel, compute thresholds for a number of regular low-density parity-check code ensembles, and verify those by Monte Carlo simulations of long channel codes. The proposed algorithm shows performance advantages with respect to an algorithm of comparable complexity from the literature

Pivoting algorithms for maximum likelihood decoding of LDPC codes over erasure channels

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A decoding algorithm for LDPC codes over erasure channels with sporadic errors

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Generalized IRA erasure correcting codes for hybrid iterative/maximum likelihood decoding

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On the performance of moderate-length non-binary LDPC codes for space communications

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Short non-binary low-density parity-check codes for phase noise channels

This paper considers the design of short non-binary low-density parity-check (LDPC) codes over finite fields of order $m$ , for channels with phase noise. In particular, $m$-ary differential phase-shift keying (DPSK)-modulated code symbols are transmitted over an additive white Gaussian noise (AWGN) channel with the Wiener phase noise. At the receiver side, non-coherent detection takes place, with the help of a multi-symbol detection algorithm, followed by a non-binary decoding step. Both the detector and the decoder operate on a joint factor graph. As a benchmark, finite length bounds and information rate expressions are computed and compared with the codeword error rate (CER) performance, as well as the iterative threshold of the obtained codes. As a result, performance within 1.2 dB from finite-length bounds is obtained, down to a CER of 10-3

From fibers to satellites: Lessons to learn and pitfalls to avoid when optical communications move to long distance free space

The paper summarizes the recent investigation on feasibility of adapting state-of-the-art coherent fiber-optics (FO) systems for Free Space Optical (FSO) scenarios. This investigation is critically dependent on the intertwined aspects of architecture, as well as device and propagation impairments (including the channel) appearing in the aforementioned systems. Towards this, the work identified the key system differences between the two systems. Particularly, the FSO channel model was investigated, impact of atmospheric turbulence on FSO was discussed and a channel series was generated. Subsequently, relevant FO techniques including coherent detection, wavelength division multiplexing and Time-Frequency packing (TFP) were reviewed. Another departure from FSO works was the emphasis on coherent reception; receiver architectures and diversity schemes were first investigated. The former strived to make fair comparison amongst the receivers considering the diverse nature of perturbation added, while the latter indicated gain in performance through increase of diversity order (2-4 dB gain). An immediate conclusion is a suggestion on adaptation of wavelength diversity when coherent receivers. The investigation also evaluated the capacity and outage of fast and slow fading channels with parameters motivated by the channel modelling work. The shaping gain was evaluated and an LDPC code design example was provided for FSO downlinks. Finally, TFP enabled a remarkable performance gain when applied to coherent detection schemes, but only marginal with direct detection. The paper concludes by pointing to the next steps that build on this investigation and the need to corroborate with measurements